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Archived

Avalanche Forecast

Feb 19th, 2016–Feb 20th, 2016
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Banff Yoho Kootenay.

While some improvement with cold temperatures on Sunday this will be mainly at lower elevations that have been affected by recent warm conditions. Continue to use caution Treeline and above until a trend away from frequent avalanche activity is seen.

Weather Forecast

Friday saw a the start of a cooling trend.  Moderate SW winds will shift to West and increase to strong overnight before shifting NW and back to the light range as the last of the precip arrives Saturday morning ahead of an approaching ridge. Saturday afternoon the ridge will build, skies should clear and temperatures drop into Sunday.

Snowpack Summary

Fresh windslabs and cornice growth in the alpine with 30 to 50 cm since the warming a week ago. A 50-100 cm slab overlies the January 6th weak layer of surface hoar, facets and sun crust and snowpack tests indicate an unstable bond between the two. The lower snowpack is facetted and quite weak in thinner areas but is more settled in thicker areas.

Avalanche Summary

There have been many close calls in the last week indicating that human triggering remains likely in many areas. Yesterday with warming temperatures there were many loose wet or slab avalanches to size 2 out of steep terrain along the divide, and a large natural avalanche out of the National Geographics in the Lake Louise backcountry.

Confidence

Avalanche Problems

Persistent Slabs

50-100 cm of snow overlies the Jan 6th layer of surface hoar, facets and sun crust. Numerous reports of avalanches triggered on this layer over the last week show that it is active. In thinner areas, isolated avalanches have scrubbed to ground.
Avoid paths that have not avalanched recently.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 3

Wind Slabs

Be mindful of cross loaded features and the lees of ridges where moderate to strong W winds have recently formed windslabs 10-40+ cm thick. If triggered, there is potential to step down to the persistent weak layer and to ground in thin areas.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use caution in lee areas. Recent wind loading has created wind slabs.

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3